Activity and functional readiness, not age, are the critical factors for second anterior cruciate ligament injury - the Delaware-Oslo ACL cohort study

Br J Sports Med. 2020 Sep;54(18):1099-1102. doi: 10.1136/bjsports-2019-100623. Epub 2020 Feb 11.


Objective: To elucidate the relationships between age, return to level I sport (RTS) within the first postoperative year, passing RTS criteria and second anterior cruciate ligament (ACL) injury.

Methods: In a prospective cohort study, 213 athletes were followed for 2 years after ACL reconstruction to record second ACL injuries. Independent variables were age, passing RTS criteria and level I RTS within the first postoperative year (vs later or no RTS). We defined passing RTS criteria as ≥90 on the Knee Outcome Survey - Activities of Daily Living Scale, global rating scale of function and quadriceps strength/hop test symmetry.

Results: The follow-up rate was >87% for all outcomes. In multivariable analysis, level I RTS within the first postoperative year and passing RTS criteria were highly associated with second ACL injury (level I RTS HR: 6.0 (95% CI: 1.6 to 22.6), pass RTS criteria HR: 0.08 (95% CI: 0.01 to 0.6)), while age was not (age HR: 0.96 (95% CI: 0.89 to 1.04)). Athletes <25 years had higher level I RTS rates in the first postoperative year (60.4%) than older athletes (28.0%). Of those who returned to level I sport in the first postoperative year, 38.1% of younger and 59.1% of older athletes passed RTS criteria.

Conclusion: High rates of second ACL injury in young athletes may be driven by a mismatch between RTS rates and functional readiness to RTS. Passing RTS criteria was independently associated with a lower second ACL rate. Allowing more time prior to RTS, and improving rehabilitation and RTS support, may reduce second ACL injury rates in young athletes with ACL reconstruction.

Keywords: anterior cruciate ligament; anterior cruciate ligament reconstruction; knee function; knee injury; return to sport.

MeSH terms

  • Activities of Daily Living
  • Adult
  • Age Factors
  • Anterior Cruciate Ligament Injuries / physiopathology*
  • Anterior Cruciate Ligament Injuries / surgery*
  • Anterior Cruciate Ligament Reconstruction
  • Female
  • Humans
  • Male
  • Muscle Strength / physiology
  • Muscle, Skeletal / physiology
  • Prospective Studies
  • Recovery of Function*
  • Recurrence
  • Return to Sport*
  • Risk Factors
  • Time Factors
  • Young Adult